In a known apparatus for the manufacture of a fancy or effect yarn of the above-indicated kind (DAS No. 24 39 732 which corresponds to U.S. Pat. No. 3 928 957), the core thread and the fancy thread are fed to the hollow spindle by a single pair of delivery rolls which rotate at the feed speed of the fancy thread and which permit slippage of the core thread. Upstream of the pair of delivery rolls, a brake means is associated with the core thread, on the intake side, for reducing the speed of the core thread to a speed corresponding to the take-up speed of the fancy yarn. However, that known apparatus can only be used to manufacture a very limited number of different designs.
It has also already been proposed, in an apparatus for the manufacture of a fancy yarn having a rotary hollow spindle, to use a drawing arrangement for the feed of fancy thread and a separate delivery arrangement for the feed of the core thread. In that arrangement, it was possible to alter the speeds of rotation of the individual rolls of the drawing arrangement, by way of coupling means and transmission assemblies, in order to alter the designs produced. However, such coupling means and transmission assemblies suffer from the disadvantage that they are comparatively sluggish in their reaction to control pulses and are therefore not suitable at the high delivery speeds which are achieved precisely in apparatuses of the kind set forth above.
The present invention is based on the problem of providing an apparatus for the manufacture of a fancy yarn, of the kind set forth above, which, while being of relatively simple construction, permits the production of a large number of different controlled fancy yarns, at a high production speed.
According to the invention, this is achieved in that the feed means comprises a drawing system for the fancy yarn having a pair of entry rolls, a pair of middle rolls and a pair of exit rolls, and a separate pair of delivery rolls for the core thread, which can be driven by the central motor by way of the control transmission, and that a respective controllable drive motor is provided for driving each of the hollow spindle and the pair of exit rolls, and a common controllable drive motor is provided for the pairs of entry and middle rolls, and that for driving the pair of take-up rolls and the pair of core thread delivery rolls, there is either a respective controllable drive motor of there is a central drive motor for driving the pair of take-up rolls by way of belt drives and the pair of delivery rolls by way of a stepless control transmission.
This apparatus can be used to manufacture controlled fancy yarns with a large number of possible variations, at high production speeds. This is to be attributed in particular to the fact that the apparatus has individual controllable drive motors, the speeds of rotation of which can be set independently of each other, and which also permit the desired speed of rotation to be very quickly attained. By virtue of using individual drive motors, the motors can be relatively small and are therefore quick to react.
Advantageously, toothed belts are used for transmitting power from the drive motors to the various pairs of rolls of the drawing system and from the central motor to the pairs of take-up and delivery rolls. The toothed belts are of very small moving mass, which also contributes to rapid adaptive alteration in their speed of rotation. In addition, they operate without slip in any range of rotary speed and have a low noise level and a damping effect, in comparison with gear transmissions.
The drive motors and the central motor are desirably voltage-controlled d.c. motors. In d.c. motors of that kind, the speed of rotation of the motor can be controlled from zero up to a maximum value, by electronic voltage control. In contrast to frequency-controlled motors, voltage-controlled d.c. motors are very quick in their operating reaction and operate with a low degree of slip when there is a change in speed of rotation. When the voltage is controlled down to zero, the motor follows in respect of its speed of rotation, down to a stationary condition. In contrast, frequency-controlled motors are unstable in the range close to zero, and expensive measures are required in order to stabilise the speed of rotation down to zero. Using motors, the speed of rotation of which can be controlled down to a stop gives the further advantage that the drive does not need to be separated by coupling means. There is therefore no need for mechanical coupling means which cause a large amount of inertia, particularly at a high level of switching operation, and must be regularly monitored and maintained on account of wear.
Using a controllable drive motor for the spindle drive permits sensitive matching control of the speed of rotation, over the entire speed range.
Preferably, the central motor serves as a pilot control motor and is connected to the other drive motors by way of electrical shafts in such a way that, upon a change in the speed of the central motor, the speeds of the other drive motors are changed in the same ratio. In this arrangement, the speeds of rotation of the individual drive motors can be individually controlled manually or by way of a program control. If however the speed of the pilot control motor changes, the speeds as to set at the controllable drive motors are also altered, in the same ratio. This is important for the purpose of always producing the same designs, irrespective of the speed of rotation of the central motor and thus the delivery and draw-off speed.